Photo-thermal energy conversion systems that use water as a working fluid may employ a black surface that absorbs visible light. The absorbed light heats the black surface. When water is brought into direct or indirect contact with the black surface, the water is heated through convection and/or conduction. Mechanical work or another type of work may then be extracted from the heated water.
Conduction and convention are not the most efficient ways to heat water. They are beset by thermal interface issues and parasitic paths, which lower the transfer of energy from the black surface to the water.
Photo-thermal energy conversion efficiency may be increased by dispersing gold nanoparticles in the water. The gold nanoparticles support a plasmon resonance when illuminated by a certain frequency light. However, since gold nanoparticles are poor light emitters, typically emitting around 1% of absorbed radiation, they heat up and transfer heat to the surrounding water by conduction and/or convection.
Higher efficiency of photo-thermal energy conversion from visible light to water is desirable.